Field
The present invention is generally related to methods and systems for generating magnetic fields, and more particularly, to methods and systems related to generating a uniform magnetic field suitable for stimulating magnetoresistive (MR) devices.
Background
Magnetic field direction sensors can be used to measure orientation of a magnetic field generating object, such as a permanent magnet, with respect to a sensing axis of a magnetic field direction sensor. Thus, when the magnet is carried on a rotating object, such as a shaft whose rotation is to be encoded, the angular displacement of the object can be determined in a non-contacting manner.
One difficulty with certain magnetic field direction sensors is that such sensors can operate in part by stimulating the sensor using a uniform magnetic field. For example, an anisotropic magnetoresistive (AMR) sensor can include magnetoresistive elements, which have a resistance that changes based on the angle of an incident magnetic field. When the magnetic field lines are not sufficiently parallel and/or the magnetic field strength is not sufficiently uniform, errors are introduced into the output of such sensors. Furthermore, stray magnetic fields can degrade sensor performance.
Therefore, a need exists for improved magnetic structures suitable for generating a uniform magnetic field.